Russian President Vladimir Putin told Syrian President Bashar al-Assad on Monday that Moscow would supply its ally with an S-300 anti-aircraft missile system, Assad's office said in a statement.

"President Putin... informed President Assad that Russia will develop the Syrian air defence systems," the Syrian presidency said in a statement.

The Russian ministry of defence confirmed on Monday it would deliver the S-300 system within two weeks as part of its response to Israel’s downing of a Russian II-20 plane last week. Fifteen Russian crew members were killed in the incident, for which Israel denies responsibility.

The delivery of the missile system had been suspended in 2013 following an Israeli request, according to a statement by the Russian ministry of defence.

“The situation has changed, and not due to our fault,” the statement said.

However, Kremlin spokesman Dmitry Peskov said Sunday that the Russian decision “is not directed against third nations,” and is primarily aimed at protecting Russian aircraft from further friendly fire.

The system would reportedly enable Syria to restrict Israeli access to its airspace, since its current anti-aircraft system is relatively outdated.

In denying responsibility for the incident, Israel blamed Syria and its allies Iran and Hezbollah.

On Sunday, Moscow formally accused Israel of “an act of criminal negligence” by failing to inform Russia of an imminent attack on targets in Syria.

"We believe that the blame for the Russian Il-20 aircraft tragedy lies entirely with the Israeli Air Force," said Russian defence ministry spokesman Major General Igor Konashenkov in a press conference in which he revealed the details of the incident.

He said the Russian plane was downed by a Syrian anti-aircraft missile off the coast of the Latakia governorate on 17 September in response to an Israeli raid on Syrian targets. Israel effectively used the plane as a cover during the attack, he added.

An Israeli military statement said the raid by its fighter jets last Monday had targeted a weapons manufacturing facility in Latakia where weapons were “about to be transferred on behalf of Iran” to Hezbollah.

The downing of the plane came just hours after Russia said there would be no assault against Syria's Idlib as the presidents of Russia and Turkey agreed to create a "demilitarised zone" in the rebel-held province.